The general objective of this project is the development of methods for exposure of details of enzymic reactions by use of the heavy-atom kinetic isotope effect. Specific objectives for the next budget period are: Initiation of a computer modeling study of the 13C/12C equilibrium and kinetic isotope effects in the action of formate dehydrogenase on formate ion. Undertaking of the theoretical interpretation of experimental 13C/12C kinetic isotope effect data on the thallium (III) ion oxidation of formic acid. Undertaking a three moiety modeling study of the action of formate dehydrogenase on formate ion using the techniques developed in the above pair of investigations.